Mosaic Agreement and Uberaba Economic Assessment

11 March 2026

Rainbow Rare Earths Limited

("Rainbow" or "the Company")

LSE: RBW

Rainbow signs Agreement with the Mosaic Company ("Mosaic") and releases Positive Economic Assessment on the Uberaba Project in Brazil

·   Economic Assessment ("EA") confirms Uberaba as a second major opportunity for Rainbow, with the project expected to be a long-life, high-margin and near-term producer of both light and heavy rare earth elements ("REE")

·    Using Rainbow's internal 10% discount rate and rare earth pricing reported by Argus Media Limited ("Argus") at March 2026, the Uberaba EA post-tax NPV₁₀ is US$916 million, with a post-tax IRR of 45%, average EBITDA of US$217 million per annum over a 30 year life-of-mine, and a pay-back of 1.7 years

·    Using the 13.5% discount rate applied in the Economic Assessment and rare earth pricing reported by Argus at 5 March 2026, the Uberaba EA post-tax NPV_13.5 is US$609 million

·    A Joint Project Development Agreement has been signed with Mosaic further to the positive financial results of the EA to pursue a pre-feasibility study ("PFS") for the Uberaba project and in the event of a positive outcome of the PFS proceed to a definitive feasibility study ("DFS")

·  Before commencement of the DFS phase the parties will negotiate Heads of Terms for a joint venture agreement and a shareholders agreement for the jointly held JV Company ("JVCo") which is agreed to be held 51% Mosaic and 49% Rainbow

·    Rainbow and Mosaic are targeting initial production for 2030, subject to further studies, regulatory approvals, financing arrangements, investment decisions, and successful project execution

·    Brazil is rapidly emerging as a rare earth hub for the Americas, with strong interest in funding and support from the USA and aligned territories

NEWS ANNOUNCEMENT

Rainbow Rare Earths announces an EA for the Uberaba project in Brazil and that it has reached an agreement with Mosaic (NYSE: MOS), the world leading Tampa, Florida-based American producer and marketer of concentrated phosphate and potash crop nutrients, to take the project forward.

The Uberaba project is similar to Rainbow's flagship Phalaborwa project in that it will entail the processing of phosphogypsum, a "waste" product that is the residue from phosphoric acid production, and will use Rainbow's intellectual property ("IP") to economically extract both light and heavy REE. By recovering critical REE from secondary sources, these projects eliminate many of the costs and risks associated with traditional REE mining projects, and as such are situated at the bottom of the industry cost curve.

George Bennett, CEO, commented: "The results of the EA confirm that Uberaba represents a major opportunity to replicate Phalaborwa as an additional high-margin and near-term REE development project, situated in the lowest-cost quartile for the industry. We are looking forward to applying all the learnings that have been made in the development of Phalaborwa's flowsheet, which provide the opportunity to develop Uberaba on a faster timescale.

The project is based in Brazil, a favourable jurisdiction which is emerging as an important hub for rare earths in the Americas and has been identified as a strategic partner in the development of supply chain independence by the USA.

We have enjoyed working alongside our partner Mosaic, who has provided important technical and operational expertise, as well as a willingness to innovate and make quick progress, and we are delighted to have signed the Joint Project Development Agreement with them to take the project forward."

Uberaba Economic Assessment

The Uberaba project is located in the Minas Gerais state of Brazil where Mosaic is currently mining phosphate rock and producing phosphoric acid for use in the fertiliser industry. The EA envisages building a processing plant on-site to process the phosphogypsum waste residue at an annual throughput of ca. 2.7 Mtpa over an initial project life of 30 years. There is excellent potential to extend this life due to the underlying long life of the phosphate feedstock at Uberaba.

The flowsheet that has been defined for the EA uses Rainbow's background IP developed for the Phalaborwa project, further supported by collaborative test work between Rainbow and Mosaic. The phosphogypsum from the Uberaba phosphoric acid process facility is treated for REE extraction, with the aim of delivering separated neodymium and praseodymium ("NdPr") oxide and a samarium, europium and gadolinium plus ("SEG+") product that is rich in medium and heavy REE, each at +99.5% purity. The chemically processed and cleaned phosphogypsum stream is then returned to the Mosaic Uberaba process facility.

Rainbow has presented the base case economics on the basis of spot rare earth prices published by Argus on 5 March 2026 assuming 100% payability for a combined NdPr product and 70% payability for the SEG+ product. The NPV is presented at a 10% discount rate, which matches the discount rate used for Rainbow's Phalaborwa project.

Key findings of the EA at current rare earth pricing:

1.   Basket price and operating costs calculated on 100% payability basis for NdPr and SEG+ weighted in-line with the feedstock grade

2.    Revenue and production statistics based on steady state throughput excluding ramp up during commissioning phase

Rare earth price sensitivity

The sensitivity to rare earth prices has been calculated by reference to a 10% increase or decrease to the base case forecast. The key financial metrics of the Uberaba Project under these different scenarios are set out below:

1.     Basket price calculated on 100% payability basis for NdPr and SEG+ weighted in-line with the feedstock grade

2.     Revenue based on steady state throughput excluding ramp up during commissioning phase

Joint Project Development Agreement with Mosaic

Further to the outstanding financial results of the EA, Rainbow and Mosaic have signed a Joint Project Development Agreement to move ahead and carry out a Pre-Feasibility Study ("PFS") for Uberaba.

On completion of a positive PFS and a decision to proceed with a Definitive Feasibility Study ("DFS"), Rainbow and Mosaic currently intend to establish a joint venture with Mosaic holding 51% and Rainbow 49%, subject to negotiation of final Heads of Terms.

Notes to the EA

The EA does not meet the standards for a scoping study under the JORC Code as it is not based on a formally designated resource. The EA is based on grade information relating to the phosphogypsum feedstock stream provided by Mosaic incorporating sampling data from the existing operations. A head grade of 0.51% TREO is used in the EA. The EA assumes recovery of 57% based on test work undertaken at Mosaic's laboratory facilities at the Uberaba site. The capital and operating costs for the EA have been developed in-line with the standards adopted for a scoping study under the JORC Code. Rainbow recognises that the assumptions upon which the EA is based and therefore the key findings of the EA may change as a result of the negotiation of the joint venture agreement and shareholders agreement for JVCo with Mosaic. The EA contains confidential information relating to both Rainbow and Mosaic and will not be published as a standalone study.

This release includes forward-looking statements. Such statements may include, but are not limited to, statements regarding the development of the Uberaba rare earths project; the expected scope, timing and results of the PFS and any subsequent DFS; the potential formation, structure or ownership of a jointly owned project company; targeted completion of Uberaba processing facility, anticipated project economics, including expected internal rate of return and payback period, production outlook, and the expected benefits of applying proprietary technology to phosophogypsum, including potential processing volumes and REE recovery. Such statements are based upon the current beliefs and expectations of the Company's management and are subject to significant risks and uncertainties. These risks and uncertainties include, but are not limited to, the results of future studies, the performance of new technologies, changes in market conditions for rare earths, the ability to negotiate and execute definitive agreements, construction and execution risks, the timing needed to complete any of the foregoing, and other risks and uncertainties described in announcements issued by the Company. Actual results may differ from those set forth in the forward-looking statements. The Company assumes no obligation to update any forward-looking statements.

THIS ANNOUNCEMENT CONTAINS INSIDE INFORMATION FOR THE PURPOSES OF ARTICLE 7 OF REGULATION 596/2014 AS AMENDED AND TRANSPOSED INTO UK LAW IN ACCORDANCE WITH THE EUROPEAN UNION (WITHDRAWAL) ACT 2018 ("UK MAR").

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Notes to Editors:

About Rainbow:

Rainbow Rare Earths aims to be a forerunner in the establishment of an independent and ethical supply chain of the rare earth elements that are driving the green energy transition. It is doing this successfully via pioneering the first commercial recovery of rare earth elements from phosphogypsum that occurs as the by-product of phosphoric acid production.  These projects eliminate the cost and risk of typical rare earth projects, which involve mining and the production of a rare earth concentrate that must be chemically cracked to form a mixed rare earth carbonate before further downstream processing. As such, Rainbow's projects can be brought into production quicker and at a lower cost than traditional hard rock mining projects.

The Company is focused on the development of the Phalaborwa Project in South Africa and the earlier stage Uberaba Project in Brazil. Rainbow's process will deliver separated rare earth oxides through a single hydrometallurgical plant on site, with a focus on the recovery of neodymium, praseodymium, dysprosium and terbium. These are critical components of the high-performance permanent magnets used in electric vehicles, wind turbines, defence and exciting new markets such as robotics and advanced air mobility.

The Phalaborwa updated interim economic study released in December 2024 has confirmed strong base line economics for the project, which has a base case NPV₁₀ of US$611 million. Given Phalaborwa is a chemical processing operation, with its resource sitting at surface in a chemically cracked form, it has a much lower operating cost than traditional rare earth mining projects, and it is therefore estimated to be one of the highest margin rare earth projects in development today.

More information is available at www.rainbowrareearths.com or by visiting the Rainbow Rare Earths Curation Showcase at: Curation Connect - Rainbow Rare Earths Showcase or https://app.curationconnect.com/company/Rainbow-Rare-Earths-90903